Identification And Control Of Pathogen Of Large Patch On Zoysia Japonica Cv.’Lanyin No.3’

As a widely used turfgrass on the sports fields in the southern China,Zoysia japonica cv.‘Lanyin No.3’has been influenced by the high frequency of diseases in south China in recent years,which has seriously affected its ornamental value and application value.In this study,seven turfs established by Zoysia japonica cv.‘Lanyin No.3’in Guangzhou and Shenzhen of Guangdong province were investigated and infected plants were collected.Pathogenic fungi was isolated by conventional tissue separation of infected plants.The species of pathogenic fungi were determined by means of morphological and molecular identification.Then the differences between the two pathogenic fungi were clarified by comparing pathogenic strain ZS-1 of large patch and pathogenic strain ZW54of brown patch in zoysiagrass in both morphological characteristics and pathogenicity.Fungicides including Heritage（50%Azoxystrobin）,Banner Maxx(156 g·L^-1Propiconazole),Medallion TL（12%Fludioxonil）,Headway（0.31%Azoxystrobin+0.75%Propiconazole）and growth regulator Primo Maxx（11.3%Trinexapac-ethyl）were selected to test the virulence of the two pathogenic fungi in laboratory and to study their effects on the prevention and control of large patch,in order to screen out fungicides with high antifungal rate and good disease control effect.Finally,the control effects and the changes of physiological characteristics of susceptible plants were examined in the process of chemical control so as to screen out the fungicides with better control effects.The main results of this study were as follows:（1）Through the investigation of 7 sites in Guangdong province,it was found that 5 of7 sites were infected with large patch,and the incidence of large patch was the highest in Shenzhen Universiade Center.The strain ZS-1 was identified as Rhizoctonia Solani by morphological identification and molecular biological identification（registration number:MH814912）.（2）Through the difference and comparison of the pathogen strains of Rhizoctonia Solani,it was found that by molecular identification,pathogenic strain ZS-1 was identified as AG-2-2 subgroup of Rhizoctonia solani,and pathogenic strain ZW54 was identified as f.sp.Sasakii subgroup of Rhizoctonia solani.The colony of strain ZS-1 was dark brown and the mycelium growth rate was slow.The colony of strain ZW54 is light and the mycelium grows fast.The results of pathogenicity test showed that the incidence and susceptibility index of strain ZW54 were 67.5%and 51.0%respectively,which were higher than strain ZS-1.（3）The indoor toxicity test of the two strains was determined,and it was found that fungicides of Heritage,Banner Maxx,Medallion TL,Headway and growth regulator Primo Maxx had an inhibitory effect on the two fungil strains.Among them,the antifungal rate of Heritage is the highest,it’s EC₅₀of strains ZS-1 and ZW54 were 5.3μg·L^-1and 0.9μg·L^-1,respectively,while that of Banner Maxx is the second,it’s EC₅₀of strains ZS-1 and ZW54were 2.3365 mg·L^-1and 0.1201 mg·L^-1,respectively.The EC₅₀of strain ZS-1 was larger,which indicated that strain ZS-1 had higher drug tolerance than strain ZW54.（4）Finally,the physiologic effect and control effect of compound treatment on the two strains of pathogen of Rhizoctonia solani showed that the application of fungicides such as Heritage,Banner Maxx,co-application of growth regulator Primo Maxx and fungicides（Primo Maxx+Heritage,Primo Maxx+Banner Maxx）had a certain control effect on Rhizoctonia solani.The control effect of single application of fungicide Heritage is the best to 43.61%,while that of single application of growth regulator Primo Maxx is the worst to20.56%.